RF ion source with dynamic volume control

ABSTRACT

Provided herein are approaches for dynamically modifying plasma volume in an ion source chamber by positioning an end plate and radio frequency (RF) antenna at a selected axial location. In one approach, an ion source includes a plasma chamber having a longitudinal axis extending between a first end wall and a second end wall, and an RF antenna adjacent a plasma within the plasma chamber, wherein the RF antenna is configured to provide RF energy to the plasma. The ion source may further include an end plate disposed within the plasma chamber, adjacent the first end wall, the end plate actuated along the longitudinal axis between a first position and a second position to adjust a volume of the plasma. By providing an actuable end plate and RF antenna, plasma characteristics may be dynamically controlled to affect ion source characteristics, such as composition of ion species, including metastable neutrals.

FIELD OF THE DISCLOSURE

The disclosure relates generally to ion sources, and more particularlyto an ion source having components for dynamically modifying plasmachamber volume.

BACKGROUND OF THE DISCLOSURE

Ion implantation is a process of introducing dopants or impurities intoa substrate via bombardment. In semiconductor manufacturing, the dopantsare introduced to alter electrical, optical, or mechanical properties.For example, dopants may be introduced into an intrinsic semiconductorsubstrate to alter the type and level of conductivity of the substrate.In manufacturing an integrated circuit (IC), a precise doping profileprovides improved IC performance. To achieve a particular dopingprofile, one or more dopants may be implanted in the form of ions invarious doses and various energy levels.

The beam line components of an ion implanter may include a series ofelectrodes configured to extract ions from the source chamber, a massanalyzer configured with a particular magnetic field where just ionshaving a desired mass-to-charge ratio are allowed to pass through theanalyzer, and a corrector magnet configured to provide a ribbon beamdirected to the platen almost orthogonally with respect to the ion beamto implant the ions into a target substrate. The ions lose energy whenthe ions collide with nuclei and electrons in the substrate and come torest at a desired depth within the substrate based on the accelerationenergy. The depth of implantation into the substrate is a function ofion energy and the mass of the ions generated in the source chamber. Insome approaches, arsenic or phosphorus may be doped to form n-typeregions in a substrate, and boron, gallium, or indium may be doped tocreate p-type regions in a substrate.

Various types of ion sources may be employed for ionizing feed gases.Such sources may be selected based on the type of plasma intended aswell as an associated ion beam profile for implantation into a targetsubstrate. One type of ion source is a hot-cathode ion source utilizingan indirectly heated cathode (IHC) to ionize a feed gas in a sourcechamber. Another type of ion source is an inductively-coupled, RF (radiofrequency) plasma ion source utilizing an RF coil to excite, throughelectromagnetic induction, a feed gas in a source chamber. A dielectricRF window separates the interior of the source chamber from the RF coil,in some cases, at atmospheric pressure. The power delivered to the RFcoil can be adjusted to control the density of the plasma and theextracted ion beam current. Due to inherent weaknesses such as lowfractionation of the monoatomic ion species, low power density and lowtemperature operation, RF ion sources face challenges.

SUMMARY

In view of the foregoing, what is needed are systems and methods fordynamically modifying plasma characteristics in an RF ion source bypositioning an end plate and RF antenna at a selected axial location ofa plasma chamber. In one approach, an ion source includes a plasmachamber having a longitudinal axis extending between a first end walland a second end wall, and an RF antenna adjacent a plasma within theplasma chamber, wherein the RF antenna is configured to provide RFenergy to the plasma. The ion source may further include an end platedisposed within the plasma chamber, adjacent the first end wall, the endplate actuated along the longitudinal axis between a first position anda second position to adjust a volume of the plasma. By providing anactuable end plate and RF antenna, dynamically controlling plasmacharacteristics is possible, as is the ability to affect ion sourcecharacteristics, such as composition of ion species including metastableneutrals.

An exemplary ion source in accordance with the present disclosure mayinclude a plasma chamber having a longitudinal axis extending between afirst end wall and a second end wall, and a radio frequency (RF) antennaadjacent a plasma within the plasma chamber, wherein the RF antenna isconfigured to provide RF energy to the plasma. The ion source mayfurther include an end plate disposed within the plasma chamber, the endplate actuated along the longitudinal axis between a first position anda second position to adjust a volume of the plasma.

An exemplary plasma chamber in accordance with the present disclosuremay include a housing having a side wall, a first end wall, and a secondend wall, wherein the second end wall includes an exit opening (e.g.,orifice or slit geometry for ion beam extraction) for delivering an ionbeam from the plasma chamber. The plasma chamber may further include aradio frequency (RF) antenna adjacent the plasma chamber, the RF antennaactuable between the first end wall and the second end wall. The plasmachamber may further include an end plate disposed within the plasmachamber, the end plate actuable along a longitudinal axis of the plasmachamber, between the first end wall and the second end wall, to adjust avolume of the plasma.

An exemplary method in accordance with the present disclosure mayinclude providing a plasma chamber having a longitudinal axis extendingbetween a first end wall and a second end wall, and positioning a radiofrequency (RF) antenna adjacent a plasma within the plasma chamber,wherein the RF antenna is actuable between the first end wall and thesecond end wall. The method may further include providing an end platedisposed along the longitudinal axis within the plasma chamber, the endplate actuable between a first position and a second position to adjusta volume of the plasma.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side cross-sectional view of an ion source in accordancewith an embodiment of the present disclosure.

FIG. 2 is a side cross-sectional view of a plasma chamber in accordancewith an embodiment of the present disclosure.

FIG. 3 is a side cross-sectional view of a plasma chamber in accordancewith an embodiment of the present disclosure.

FIG. 4A is a side cross-sectional view of a plasma chamber in accordancewith an embodiment of the present disclosure.

FIG. 4B is a side cross-sectional view of the plasma chamber of FIG. 4Ain accordance with an embodiment of the present disclosure.

FIG. 5A is a side cross-sectional view of a plasma chamber in accordancewith an embodiment of the present disclosure.

FIG. 5B is a side cross-sectional view of the plasma chamber of FIG. 5Ain accordance with an embodiment of the present disclosure.

FIG. 6 is a flowchart illustrating an exemplary method in accordancewith embodiments of the present disclosure.

The drawings are not necessarily to scale. The drawings are merelyrepresentations, not intended to portray specific parameters of thedisclosure. The drawings are intended to depict exemplary embodiments ofthe disclosure, and therefore are not be considered as limiting inscope. In the drawings, like numbering represents like elements.

DETAILED DESCRIPTION

A system and method in accordance with the present disclosure will nowbe described more fully hereinafter with reference to the accompanyingdrawings, where embodiments of the system and method are shown. Thesystem and method may be embodied in many different forms and are not tobe construed as being limited to the embodiments set forth herein.Instead, these embodiments are provided so this disclosure will bethorough and complete, and will fully convey the scope of the system andmethod to those skilled in the art.

For the sake of convenience and clarity, terms such as “top,” “bottom,”“upper,” “lower,” “vertical,” “horizontal,” “lateral,” and“longitudinal” will be used herein to describe the relative placementand orientation of these components and their constituent parts, withrespect to the geometry and orientation of a component of asemiconductor manufacturing device as appearing in the figures. Theterminology will include the words specifically mentioned, derivativesthereof, and words of similar import.

As used herein, an element or operation recited in the singular andproceeded with the word “a” or “an” are understood as potentiallyincluding plural elements or operations as well. Furthermore, referencesto “one embodiment” of the present disclosure are not intended to beinterpreted as precluding the existence of additional embodiments alsoincorporating the recited features.

As stated above, provided herein are approaches for dynamicallymodifying plasma volume in an ion source chamber by positioning an endplate and radio frequency (RF) antenna at a selected axial location. Inone approach, an ion source includes a plasma chamber having alongitudinal axis extending between a first end wall and a second endwall, and an RF antenna adjacent a plasma within the plasma chamber,wherein the RF antenna is configured to provide RF energy to the plasma.The ion source may further include an end plate disposed within theplasma chamber, adjacent the first end wall, the end plate actuatedalong the longitudinal axis between a first position and a secondposition to adjust a volume of the plasma. By providing an actuable endplate and RF antenna, dynamic control of plasma characteristics isachievable, as is the modification of ion source characteristics, suchas composition of ion species, plasma density, electron temperature, andalso including metastable neutrals.

Furthermore, approaches herein provide an end plate made of either anelectrically conducting material (e.g. doped Si, doped SiC, Aluminum,Tungsten) or an insulating material (e.g., Si, SiC, ceramics). The endplate may also be used as a gas baffle for introducing a dopant gaseither uniformly or along an outer region (e.g., closer to the RF coil)for improved power coupling. In some embodiments, the end plate can bebiased, either positively or negatively, to control the plasmacharacteristics further. For example, the end plate can be RF biasedusing either low frequency (kHz range) or high frequency (MHz) range. Inother examples, plasma volume may be set to a maximum if molecular ionspecies are intended, such as BF₂ ⁺, N₂ ⁺, dimers (P₂ ⁺, As₂ ⁺, B₂ ⁺),or trimers (P₃ ⁺, As₃ ⁺). In contrast, if monoatomic ion species, suchas B⁺ or N⁺ are desired, the plasma chamber volume is set to a minimumby moving the end plate towards the exit opening (e.g., orifice or slit)of the plasma chamber in order to maximize the power density and changethe ratio of the plasma volume to boundary area.

In addition, a bias voltage can be applied to the end plate in order tofurther control the plasma characteristics. The end plate can befabricated with the desired dopant containing material (e.g. boroncarbide, LaB₆, GaN). In such cases, the desired dopant material can besputtered via ion bombardment by negative bias on the end plate, ionizedin the plasma, and then extracted as an ion beam. This phenomenon canincrease the desired ion beam current. In other cases, where dopantmaterial needs special delivery, such as when Ga is a liquid metal andtherefore hard to feed into the plasma chamber for ionization, an endplate having the desired dopant material sputtered via ion bombardmentcan be used to create and extract the desired ion species. Thepositively bias voltage can be applied to the end plate, thus alteringthe plasma potential and electron temperature and, serving as analternative way to tune the plasma parameters for an optimal condition.Also, RF bias can be applied to the end plate, either kHz range or MHzrange, to establish a self-bias voltage (e.g., negative) on the endplate. The benefit of RF bias on the end plate is the ability to useelectrically conducting and/or electrically insulating materials as anend plate.

Furthermore, approaches herein may be applied to a negative ion source.For example, a hot plasma characteristics in a driver region of thenegative ion source can be adjusted by positioning and bias voltage ofthe end plate and the RF antenna. For H⁻ beam generation, high-densityand high Te (electron temperature) plasma may be generated in the driverregion. In addition, an extra electrode with negative voltage bias canbe added near the end plate to generate additional surface-produced H⁻ions with appropriate materials such as tantalium. For other negativeion species (e.g. He⁻, O⁻, F⁻, Cl⁻), the plasma chamber volume couldsimilarly be adjusted for optimal effect.

Referring now to FIGS. 1-2, an exemplary embodiment demonstrating an ionsource 100 for dynamically modifying plasma volume in an ion sourcechamber in accordance with the present disclosure is shown. The ionsource 100 represents an apparatus containing, among other components, aplasma chamber 110 including a housing 112, wherein the plasma chamber110 producing a plasma 114 and allowing extraction of an ion beam 116through an exit aperture 139 (e.g., an extraction orifice or slit). Theplasma chamber 110 includes an end plate 113 disposed therein, foradjusting the volume of the plasma 114. The plasma chamber 110 isconfigured to receive a flow of gas 117, and generate ions therein. Theion source 100 may also comprise a power source and a set of electrodesdisposed near the plasma chamber 110. In some embodiments, the ionsource 100 may include a voltage source 160 and one or more extractionelectrodes 121 and 122, wherein the voltage source is electricallycoupled to the housing 112, for example as demonstrated in FIG. 1, or tothe end plate 113, for example as demonstrated in FIG. 2.

In various embodiments, different species may be introduced via the gas117. Examples of the source and/or additional material may includeatomic or molecular species containing boron (B), carbon (C), oxygen(O), germanium (Ge), phosphorus (P), arsenic (As), silicon (Si), helium(He), neon (Ne), argon (Ar), krypton (Kr), nitrogen (N), hydrogen (H),fluorine (F), and chlorine (Cl). Those of ordinary skill in the art willrecognize the above listed species are non-limiting, and other atomic ormolecular species may also be used. Depending on the application(s), thespecies may be used as the dopants or the additional material. Inparticular, one species used as the dopants in one application may beused as the additional material in another application, or vice-versa.

Although not shown, the ion source 100 may further include one or moremagnets formed around the plasma chamber 110. In some embodiments, theion source 100 includes a filter magnet (e.g., transverse magnet) withinthe housing 112 for producing an electron filter field within theplasma. In other embodiments, the ion source 100 may further include aplurality of pole cusp magnets provided adjacent the filter magnet.

Referring now to FIG. 2, the plasma chamber 110 according to exemplaryembodiments will be described in greater detail. As shown, the plasmachamber 110 includes a housing having a first side wall 132, a secondside wall 134, a first end wall 136, and a second end wall 138, whereinan exit aperture 139 (e.g., opening or slit) is formed through thesecond end wall 138 to allow extraction of the ion beam 116 therefrom.In cases where the plasma chamber 110 is cylindrical, one willappreciate the first side wall 136 and the second side wall 138 may beconsidered joined/continuous.

The plasma chamber 110 further includes a radio frequency (RF) antenna,shown as RF antenna 140, (e.g., a coil) provided adjacent an exteriorsurface 142 of the plasma chamber 110, wherein the RF antenna 140 isconnected to a RF supply (not shown). The RF antenna 140 is provided toexcite, through electromagnetic induction, the gas in the plasma chamber110, and to control the density of the plasma 114 and a current of theextracted ion beam 116. In exemplary embodiments, the RF antenna 140 isactuable along the exterior surface 142, between the first end wall 136and the second end wall 138, for example, as indicated by arrow 144. Theplasma chamber 110 may include an RF window 146 formed along at leastone of the first side wall 132 and the second side wall 134, wherein theRF antenna 140 is disposed adjacent the RF window 146. During operation,ions are produced in the plasma chamber 110 by inductively coupling RFpower from the RF antenna 140 into the gas within the plasma chamber110. In one embodiment, RF power frequency can vary, for example,between 2 MHz 40 MHz. The ions are then extracted through the exitaperture 139 as the ion beam 116. The ions can be positive or negativein various embodiments.

As further shown, the plasma chamber 110 includes the end plate 113disposed therein. The end plate 113 is actuable along the longitudinalaxis ‘L’ of the plasma chamber 110, between the first end wall 136 andthe second end wall 138, to adjust a volume of the plasma 114 containedtherein. In one embodiment, end plate 113 includes a first section 113-Adisposed within the plasma chamber 110, the first section having a firstsurface 148 exposed to the plasma 114. As shown, the first surface 148may be curved to motivate the plasma 114 towards the longitudinal axis‘L.’ The first section 113-A further includes a second surface 150,opposite the first surface 148, the second surface 150 remaininggenerally unexposed to the plasma 114. As further shown, and firstsection 113-A includes first and second ends 152, 154 adjacentrespective side walls 132 and 134 of the plasma chamber 110. Althoughnot shown, in some embodiments, the first and second ends 152, 154 arein contact with an inner surface 166 of the plasma chamber 110 to form aseal therebetween.

The end plate 113 further includes a second section 113-B coupled to thefirst section 113-A, for example, in a perpendicular arrangement. Asshown, the second section 113-B extends outside of the plasma chamber110, beyond the first end wall 136. The second section 113-B may beprovided with a vacuum feedthrough 157 for coupling and sealing thesecond section 113-B of the end plate 113 to the first end wall 136. Thevacuum feedthrough 157 provides a vacuum seal as well as motion andelectrical isolation for bias voltage. Although not shown, the secondsection 113-B may be driven by a mechanical device configured to actuatethe end plate 113 to an intended axial position within the plasmachamber 110.

During operation, the end plate 113 may be actuated from a firstposition, for example, proximate the first end wall 136, to a secondposition closer to the exit aperture 139. As the end plate 113 movestowards the second end wall 138, the first section 113-A increases adensity and temperature of the plasma 114 by reducing a volume availableto the plasma 114 within the plasma chamber 110. In the first position,the plasma volume is set to the maximum, for example, in the casemolecular ion species are desired (e.g. BF₂ ⁺, N₂ ⁺, dimers, trimers,etc.). In contrast, in the case monoatomic ion species (e.g. B⁺, N⁺, C⁺,etc.) are desired, the plasma chamber volume is set to the minimum bymoving the end plate 113 towards the second end wall 138 in order tomaximize the power density and change the ratio of plasma volume toboundary area.

In some embodiments, the second section 113-B may be further coupled toa voltage source 160 for providing a voltage (negative or positive) tothe end plate 113. The voltage source 160 may provide a bias voltage tothe end plate 113 in order to further control the plasmacharacteristics. For example, the end plate 113 may be negatively biasedfor electrostatic confinement, and positively biased for plasmapotential control. Furthermore, in the case the end plate 113 contains adopant element such as Boron or Phosphorous, the beam current may beincreased. The bias voltage on the end plate 113, whether negative DC orRF, causes sputtering of the end plate. Sputtered dopant elements arethen ionized in the plasma 114, and extracted as an ion beam 116. UnlikeDC bias, RF bias polarity cannot be switched between positive andnegative, and the RF net bias (self-bias) is generally negative. RF biasis useful for sputtering the dopant material included in electricallyinsulating materials.

Additionally, the RF antenna 140 may simultaneously move towards thesecond end wall 138 along the exterior surface 142 of the plasma chamber110. In one embodiment, the end plate 113 and the RF antenna 140 maymove together in a fixed or proportional amount. In another embodiment,the end plate 113 and the RF antenna 140 may move independent of oneanother.

In some embodiments, the end plate 113 can be made of either anelectrically conducting material, such as doped Si, doped SiC, Aluminum,or Tungsten, or an insulating material, such as Si, quartz or ceramics.In addition, in the case the end plate 113 is made of an electricallyconducting material, the end plate 113 may be electrically biased tofurther control characteristics of the plasma, as described above. TheRF bias on the end plate 113 can be applied to electrically conductingand insulating materials.

Turning now to FIG. 3, a plasma chamber 210 according another exemplaryembodiment of the disclosure will be described in greater detail. Inthis embodiment, the end plate 213 may also be used as a gas baffle forintroducing a dopant gas 217 to the plasma 214. Specifically, the endplate 213 is provided with a plurality of internal fluid passageways 270extending between first and second ends 252, 254 for introducing thedopant gas 217 to the plasma 214 within the plasma chamber 210. Asshown, the end plate 213 includes first and second sections 213A-B,wherein the second section 213-B initially receives and transports thedopant gas 217 via a central orifice 272. The dopant gas 217 is thentransported to the plurality of fluid passageways 270, where the dopantgas 217 is conducted to the plasma 214. In one embodiment, the pluralityof internal fluid passageways 270 are evenly spaced between the firstand second ends 252, 254 of the end plate 213 so as to more uniformlydeliver the dopant gas 217 to the plasma 214. Furthermore, bypositioning the internal fluid passageways 270 within the end plate 213,the dopant gas 217 may be introduced into the plasma 214 in an areacloser to an RF antenna 240, thus improving power coupling.

Similar to the plasma chamber 110 shown in FIG. 2, the plasma chamber210 further includes the RF antenna 240 adjacent an RF window 246 alongan exterior surface 242 of the plasma chamber 210, wherein the RFantenna is connected to a RF supply (not shown). In exemplaryembodiments, the RF antenna 240 is actuable between a first end wall 236and a second end wall 238, for example, as indicated by arrow 244.

Furthermore, the end plate 213 is actuable along the longitudinal axis‘L’ of the plasma chamber 210, between the first end wall 236 and thesecond end wall 238, to adjust a volume of the plasma 214 containedtherein. The second section 213-B may be coupled to a mechanical device(not shown) for actuating the end plate 213 to an intended axialposition within the plasma chamber 210. In some embodiments, the secondsection 213-B may be further coupled to a voltage source 260 forproviding a voltage (e.g., negative or positive DC, pulsed DC or RF) tothe end plate 213.

During operation, the end plate 213 may be actuated from a firstposition, for example, proximate the first end wall 236, to a secondposition closer to an exit aperture 239. As the end plate 213 movestowards the second end wall 238 along the longitudinal axis ‘L,’ thefirst section 213-A pushes against the plasma 214, moving the plasma 214towards the second end wall 238. As a result, a volume of the plasma 214decreases, causing a density and temperature of the plasma 214 withinthe plasma chamber 210 to increase. Conversely, the end plate 213 mayalso be actuated towards the first end wall 236 to increase a volume ofthe plasma 214, causing the density and temperature of the plasma 214within the plasma chamber 210 to decrease. As such, the position of theend plate 213 can be dynamically adjusted to optimize ion species and topromote the intended negative ion species within the plasma 214.

Additionally, the RF antenna 240 may simultaneously move towards thesecond end wall 238 along the exterior surface 242 of the plasma chamber210. In one embodiment, the end plate 213 and the RF antenna 240 maymove together in a fixed or proportional amount. In another embodiment,the end plate 213 and the RF antenna 240 are independently actuable.

Turning now to FIGS. 4A-B, a plasma chamber 310 according anotherexemplary embodiment of the disclosure will be described in greaterdetail. In this embodiment, the plasma chamber 310 may be part of anegative ion source. As such, the plasma chamber 310 includes a firstregion 311 (e.g., a hot plasma region), also known as a driver region,and a second region 316 (e.g., a colder region) separated, generally, bymagnetic field lines 315 generated by a filter magnet 328 disposedproximate the plasma chamber 310. In some embodiments, the filter magnet328 can be a permanent magnet or coil magnet.

As shown, the plasma chamber 310 further includes an RF antenna 340(e.g., a coil) provided adjacent an RF window 346 along an exteriorsurface 342 of the plasma chamber 310, the RF antenna 340 connected toan RF supply (not shown). In exemplary embodiments, the RF antenna 340is actuable between a first end wall 336 and a second end wall 338, forexample, along the exterior surface 342 of the plasma chamber 310, asindicated by arrow 344.

In exemplary embodiments, the end plate 313 may be actuable along thelongitudinal axis ‘L’ of the plasma chamber 310, between the first endwall 336 and the second end wall 338, to adjust a volume of the plasma314 contained therein. For example, the end plate 313 may be actuatedfrom a first position proximate the first end wall 336, as demonstratedin FIG. 4A, to a second position further along the longitudinal axis ‘L’within the plasma chamber 310, as demonstrated in FIG. 4B. As the endplate 313 moves towards the second end wall 338, e.g., by a distance‘D,’ the end plate 313-A increases a density and temperature of theplasma 314 by reducing a volume of the plasma 314 within the plasmachamber 310. As a result, the hot plasma within the first region 311causes a higher electron temperature and density, thus producing moreradicals present in the colder region, second region 316. The radicalsare then converted to negative ions and extracted from the plasmachamber 310.

In one example, the plasma chamber 310 may generate an H⁻ ion beam. Theend plate 313 may be positioned in the position shown in FIG. 4B topromote high-density and high electron temperature (Te) of the plasma314. A negative DC voltage can be simultaneously applied by the voltagesource 360 to the end plate 313 to generate the hyper-thermal neutrals,thus promoting H⁻ generation via dissociative attachment. In otherembodiments, the voltage source may provide a negative pulsed DC or RFbias). For other negative ion species, such as He⁻, O⁻, Cl⁻, the volumeof the plasma chamber 310 may be individually adjusted to promoteoptimal ion generation specific to individual ion species.

In some embodiments, the RF antenna 340 may simultaneously move towardsthe second end wall 338 along the exterior surface 342 of the plasmachamber 310. In one embodiment, the end plate 313 and the RF antenna 340may move together in a fixed or proportional amount. In anotherembodiment, the end plate 313 and the RF antenna 340 are independentlyactuable.

Turning to FIGS. 5A-B, a plasma chamber 410 according to anotherexemplary embodiment of the disclosure will now be described. Similar tothe plasma chambers shown in FIGS. 1-4, the plasma chamber 410 includesan end plate 413 actuable along a longitudinal axis ‘L’ of the plasmachamber 410, between a first end wall 436 and a second end wall 438, toadjust a volume of a plasma 414 contained therein. During operation, theend plate 413 may be actuated from a first position, demonstrated inFIG. 5A, to a second position, demonstrated in FIG. 5B. As the end plate413 moves towards the second end wall 438, the end plate 413 increases adensity and temperature of the plasma 414 by reducing a volume of theplasma 414 within the plasma chamber 410. Conversely, the end plate 413may also be actuated towards the first end wall 436 to increase a volumeof the plasma 414, causing the density and temperature of the plasma 414within the plasma chamber 410 to decrease. As such, the position of theend plate 413 can be dynamically adjusted to optimize ion species and topromote the intended negative ion species within the plasma 414.

In this embodiment, an RF antenna 440 (e.g., a coil) and an RF window446 are provided within the end plate 413. The RF antenna 440 willtherefore simultaneously move towards the second end wall 438 with theend plate 413. As shown, the RF window 446 is adjacent to and generallyexposed to the plasma 414 within the plasma chamber 410. The plasmachamber 410 may further include a vacuum feedthrough 457 forcoupling/sealing the end plate 413 to the first end wall 436. In someembodiments, the vacuum feedthrough includes an expandable baffle forallowing a flexible seal between the end plate 413 and the first endwall 432 of the plasma chamber 410.

Referring now to FIG. 6, a flow diagram illustrating an exemplarymethod, method 500, for adjusting a volume of a plasma chamber inaccordance with the present disclosure is shown. The method 500 will bedescribed in conjunction with the representations shown in FIGS. 1-5B.

Method 500 includes providing a plasma chamber having a longitudinalaxis extending between a first end wall and a second end wall, as shownin block 501. In some embodiments, the plasma chamber further includesfirst and second side walls, and an exit aperture formed through thesecond end wall. In some embodiments, the plasma chamber contains aplasma. In some embodiments, a vacuum feedthrough couples the secondsection of the end plate to the second end wall of the plasma chamber.

Method 500 further includes positioning an RF antenna adjacent theplasma within the plasma chamber, as shown at block 503. In someembodiments, the RF antenna is actuable between the first and second endwalls of the plasma chamber. In some embodiments, the RF antenna is acoil. In some embodiments, the plasma chamber further includes an RFwindow formed along a sidewall of the plasma chamber, wherein the RFantenna is disposed adjacent the RF window.

Method 500 further includes providing an end plate disposed along thelongitudinal axis within the plasma chamber, as shown at block 505,wherein the end plate is actuable between a first position and a secondposition to adjust a volume of a plasma. In some embodiments, the endplate includes a first section disposed within the plasma chamber, thefirst section extending between the first and second side walls of theplasma chamber. The end plate further includes a second section coupledto the first section, the second section extending outside of the plasmachamber.

Method 500 may further include an optional process of applying a voltageto the end plate, as shown at block 507. In some embodiments, thevoltage is applied to the second section of the end plate by a voltagesource. In some embodiments, the voltage to the end plate can be DC(positive/negative), pulsed DC (positive/negative) or RF.

In view of the foregoing, at least the following advantages are achievedby the embodiments disclosed herein. A first advantage includes theability to provide positive and negative ion sources with adjustablevolume control in existing implantation tools. A second advantageincludes the ability to provide additional control knobs in existingprocessing tools for controlling plasma characteristics. A thirdadvantage includes the applicability to multiple species such as B⁺, BF₂⁺, P⁺, and As⁺, molecular species, dimers, trimers, as well as negativeion species.

While certain embodiments of the disclosure have been described herein,the disclosure is not limited thereto, as the disclosure is as broad inscope as the art will allow and the specification may be read likewise.Therefore, the above description are not to be construed as limiting.Those skilled in the art will envision other modifications within thescope and spirit of the claims appended hereto.

The invention claimed is:
 1. An ion source comprising: a plasma chamberhaving a longitudinal axis extending between a first end wall and asecond end wall; a radio frequency (RF) antenna adjacent a plasma withinthe plasma chamber, the RF antenna configured to provide RF energy tothe plasma; and an end plate actuated along the longitudinal axisbetween a first position and a second position to adjust a volume of theplasma, the end plate including a first section disposed within theplasma chamber and a second section coupled to the first section,wherein the second section extends outside of the plasma chamber, andwherein the first section extends to a sidewall of the plasma chamber.2. The ion source of claim 1, further comprising a voltage sourcecoupled to the end plate.
 3. The ion source of claim 1, the end plateincluding a curved surface in contact with the plasma.
 4. The ion sourceof claim 1, wherein the end plate includes a set of internal fluidpassageways for delivering a gas into the plasma chamber.
 5. The ionsource of claim 1, further comprising a filter magnet positionedproximate the plasma chamber.
 6. The ion source of claim 1, furthercomprising an exit aperture formed through a first end wall of theplasma, the exit aperture disposed along the longitudinal axis.
 7. Theion source of claim 1, further comprising a vacuum feedthrough couplingthe second section of the end plate to a second end wall of the plasmachamber.
 8. The ion source of claim 1, the sidewall of the plasmachamber comprising an RF window, wherein the RF antenna is disposedadjacent the RF window.
 9. A plasma chamber for generating a plasma, theplasma chamber comprising: a housing comprising a side wall, a first endwall, and a second end wall, wherein the second end wall includes anexit aperture for delivering an ion beam from the plasma chamber; aradio frequency (RF) antenna adjacent the plasma, the RF antennaactuable between the first end wall and the second end wall; and an endplate actuable along a longitudinal axis of the plasma chamber, betweenthe first end wall and the second end wall, to adjust a volume of theplasma, the end plate including a first section disposed within theplasma chamber and a second section coupled to the first section,wherein the second section extends outside of the plasma chamber, andwherein the first section extends to a sidewall of the plasma chamber.10. The plasma chamber of claim 9, wherein the first section of the endplate has a first surface exposed to plasma within the plasma chamber,and a second surface opposite the first surface, wherein the secondsurface is unexposed to the plasma within the plasma chamber.
 11. Theplasma chamber of claim 9, wherein the end plate is electrically coupledto a voltage source.
 12. The plasma chamber of claim 9, wherein the RFantenna is disposed along an exterior surface of the side wall of theplasma chamber.
 13. The plasma chamber claim 9, wherein the RF antennais disposed within the end plate.
 14. The plasma chamber of claim 9,wherein the end plate includes a set of fluid passageways forintroducing a gas to the plasma chamber.
 15. The plasma chamber of claim10, further comprising: an RF window disposed along the side wall of theplasma chamber, wherein the RF antenna is disposed adjacent the RFwindow; and a filter magnet proximate the RF window.
 16. A method foradjusting a volume of plasma within a plasma chamber, the methodcomprising: providing a plasma chamber having a longitudinal axisextending between a first end wall and a second end wall; positioning aradio frequency (RF) antenna adjacent a plasma within the plasmachamber, the RF antenna actuable between the first end wall and thesecond end wall; and providing an end plate actuable along thelongitudinal axis between a first position and a second position toadjust a volume of the plasma, the end plate including a first sectiondisposed within the plasma chamber and a second section coupled to thefirst section, wherein the second section extends outside of the plasmachamber, and wherein the first section extends to a sidewall of theplasma chamber.
 17. The method of claim 16, further comprising actuatingthe end plate and the RF antenna towards the second end wall to increasea density of the plasma, the second end wall including an exit aperturefor delivering an ion beam from the plasma chamber.
 18. The method ofclaim 16, further comprising applying a voltage to the end plate. 19.The method of claim 16, further comprising introducing a gas to theplasma chamber through a set of internal fluid passageways formedthrough the end plate.